Interviews with fishers reveal a long-term record of species change.

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The world is losing species at a staggering pace, but because of inconsistencies in scientific record keeping, we just don’t know how bad it really is in some places. Take the Philippines, for example. The country is home to one of the world’s most biodiverse—and most threatened—marine ecosystems. But there, wildlife censuses are a relatively new tool. Scientists assume that Filipino seas have been losing species, but without data it’s hard to say for sure.

While scientists may not have been paying close attention, Filipino fishermen sure were. So, from 2012 to 2014, researcher Margarita N. Lavides and her team interviewed more than 2,600 fishers from 61 villages about their current and historical catch rates, focusing on reef-based finfish. By mining the fishers’ memories, Lavides produced a record of species loss in Filipino seas that stretches back nearly seventy years.

Through the fishermen’s testimonies, Lavides found that at least 59 different kinds of finfish all but disappeared from their catches between the 1950s and today. The researchers were able to precisely identify the species of 42 of these, while the fishers’ descriptions only gave enough detail to figure out higher taxonomic classifications for the rest.

The five most depleted species were the green bumphead parrotfish, the African pompano, the mangrove red snapper, the humphead wrasse, and the giant grouper. The population levels for these fish declined between 88 percent (for the parrotfish) and 64 percent (for the snapper).

Lavides’ findings align well with the broad trends seen elsewhere in the region.

For the past half-century, the Philippines’ coral reefs have been under intense fishing pressure. Coral reefs that were highly productive in the 1950s and 1960s were overfished by the 1980s. By the 1990s, the amount of fish that could be taken from Filipino reefs had dropped by half.

Traditional scientific surveys of nearby marine habitats show sharp decreases in biomass for seafloor species, and overwhelming declines in abundance or geographic range for the vast majority of large-bodied fish.

By drawing on fishers’ memories, scientists now have a clearer picture of how the reef ecosystem has changed.

This is not the first ecological study to rely on interviews, but it is perhaps unique in its scale, says social scientist Amy Freitag, who was not involved in the study. “Usually these kinds of studies are on the order of 15 to 30 people, at best,” she says. By speaking with so many people, Lavides was able to analyze the data quantitatively rather than qualitatively.

But the value from this study stems not only from establishing a historical biodiversity baseline for comparison with modern surveys. “Stock assessments tend to get a skeptical eye from most fishermen,” says Frietag. “Anytime you get your stakeholders involved, they trust [the data], and use it, and value it more.”

By involving fishermen in the study, Lavides may have established grounds for greater potential for collaboration when it comes to implementing conservation initiatives down the line.